Half tone laser recording apparatus

Abstract

A laser recording recording apparatus including a semiconductor laser as a light source and enabling half-tone recording. The apparatus includes a recording medium moving in a sub-scanning direction, M semiconductor lasers arranged along the sub-scanning direction at a slight distance to one another and enabled to be independently modulated according to image signals, where M is an integral number of at least two, a deflector for deflecting M laser beams emitted from the M semiconductor lasers toward the recording medium and for scanning the beams in a main scanning direction, and an image forming optical system for imaging the deflected laser beams at a predetermined distance between one another along the sub-scanning direction. An exposure pattern on the recording medium is represented by a pixel matrix comprising N×L micro pixels, where N is the number of micro pixels with respect to said main scanning direction and L is the number of micro pixels with respect to the sub-scanning direction, and the exposure pattern is varied according to a density information included in the image signal thereby to record half-tone, where L is an integral number of times M.

What is claimed is: 
     
       1. A laser recording apparatus comprising: a transporting means for transporting a recording medium in a sub-scanning direction;   M semiconductor lasers arranged along said sub-scanning direction at a slight distance to one another, M being an integral number from two to sixteen;   a converting means for converting an image information into a recording information comprising a plurality of pixel data each having a density data;   a deflector for deflecting M laser beams emitted from said M semiconductor lasers toward said recording medium;   a scanning means for scanning said deflected M laser beams on said recording medium at a predetermined distance between one another simultaneously in a main scanning direction by controlling said deflector; and   an exposing means for exposing said recording information on said recording medium through said scanning means and said transporting means, each of said pixel data in said recording information being represented by a recording pattern of pixel matrix comprising N×L micro pixels, N being an integral number from two to twenty representing the number of micro pixels with respect to said main scanning direction, L being a multiple number of M from one time to sixteen times representing the number of micro pixels with respect to said sub-scanning direction, said exposing means for controlling said emission of each of M semiconductor lasers in order to vary said recording pattern according to said density data to record half-tone, and a distance between each of said micro pixels in said sub-scanning direction being equal to said predetermined distance between each of said deflected M laser beams on said recording medium.   
     
     
       2. An apparatus according to claim 1 wherein L is equal to M. 
     
     
       3. An apparatus according to claim 1, wherein said exposing means exposes said recording pattern from micro pixels in a central area of said pixel matrix with respect to said sub-scanning direction with first priority, according to an elevation of said density data. 
     
     
       4. An apparatus according to claim 1, wherein said exposing means exposes said recording pattern from central micro pixels in said sub-scanning direction with respect to said main scanning direction and then micro pixels adjacent to said central micro pixels with respect to said main scanning direction, according to an elevation of said density data. 
     
     
       5. An apparatus according to claim 1, wherein said converting means converts an image information into a recording information comprising a plurality of pixel data each having a multi-level density data. 
     
     
       6. An apparatus according to claim 1, wherein said converting means converts an image information into a recording information comprising a plurality of pixel data each having a binary density data. 
     
     
       7. A recording apparatus for generating an image, comprising: a rotatable recording medium having a cylindrical shape with a longitudinal axis and a circumference, said recording medium having a photosensitive surface, said recording medium having a main scanning direction parallel to the longitudinal axis and a sub-scanning direction parallel to the circumference;   a semiconductor laser array generating a plurality of laser beams (M) aimed at the recording medium along the sub-scanning direction;   an image forming means for forming the laser beams on the recording medium in a two-dimensional pixel pattern of micro-pixels forming a half tone pattern, said pixel pattern having rows (L) and columns (N), said number of rows (L) is an integral multiple of the number of laser beams (M);   recording medium rotating means for rotating the recording medium about the longitudinal axis at a recording medium rate;   deflecting means for deflecting the laser beams toward the recording medium; and   a deflecting rotating means for rotating the deflecting means at a deflecting rate corresponding to the recording medium rate, said pixels pattern being deflected across the main scanning direction of the recording medium completing each main scanning direction line of the image until a complete photoelectric image is formed on the recording medium representing the image.   
     
     
       8. A recording apparatus according to claim 7, wherein the image forming means comprises: an anamorphic lens having in which focal distances differ along the main scanning direction and the sub-scanning direction, said anamorphic lens creating the two-dimensional pixel pattern;   
     
     
       9. A recording apparatus according to claim 7, further comprising: focusing means for focussing the laser beams.   
     
     
       10. A recording apparatus according to claim 9, wherein the focussing means comprises: a collimator lens for collimating the laser beams;   a cylinder lens receiving the collimated laser beams and directing the laser beams onto the deflecting means, said deflecting means deflects the laser beams through the image forming means, and the image forming means forms the pixel pattern on the recording medium.   
     
     
       11. A recording apparatus according to claim 7, wherein the deflecting means is a polygonal mirror. 
     
     
       12. A recording apparatus according to claim 7, wherein the number of laser beams (M) and the number of rows (L) are set to three and the number of columns (N) is set to three, said laser beams including an upper, center and lower laser beam, the center laser beam impinging on the recording medium at a normal angle and a micro-pixel resulting from the center laser beam not distorted by curvature. 
     
     
       13. A recording apparatus according to claim 12, further comprising: a pixel pattern scheme for mapping the pixel pattern for each pixel density, said pixel pattern scheme forming said micro-pixels with the center laser beam for lower densities, wherein said images having low densities will be formed using mostly the center laser beam, which is normal to the recording medium, and the low density image is not distorted by curvature.   
     
     
       14. A recording apparatus according to claim 7, wherein the number of laser beams (M) and the number of rows (L) are set to five and the number of columns (N) is set to three, said laser beams including central laser beams located in a region of the center rows of the pixel pattern, the central laser beams impinging on the recording medium at a normal angle and a micro-pixel resulting from the central laser beams not being distorted by curvature. 
     
     
       15. A recording apparatus according to claim 14, further comprising: a pixel pattern scheme for mapping the pixel pattern for each pixel density, said pixel pattern scheme forming said micro-pixels with the central laser beams for low density images, said low density images being formed using the central laser beams, being normal to the recording medium, the low density image not being distorted by curvature.